The present invention relates to a rear axle suspension for a motor vehicle with a wheel guide member directly retained at the wheel carrier that includes a first wheel-outer guide arm and a second wheel-inner guide arm and in which both guide arms are pivotally connected at the vehicle body by way of elastic joints, whereby one joint of the first guide arm is constructed yielding longitudinally and forms together with the further elastic joint of the second guide arm an approximately transversely extending wheel guide axis of rotation and an imaginary wheel guide pole to the rear of the axis of rotation of the wheel and outside of wheel track.
A rear axle suspension with a guide body directly connected with a wheel carrier is disclosed in the DE-OS 32 42 930 which includes a wheel-inner and a wheel-outer guide arm. The wheel-outer guide arm is retained on the body side in an axially movable bearing support whereby the wheel-inner guide arm is supported in a joint. This guide arm consists of a connecting member elastically retained at the guide body and having a vertical axis of rotation so that with forces acting on the wheel an elastic kinematic wheel position change can take place. A wheel suspension having the same manner of operation has become known from the DE-PS 26 45 272 whose wheel-outer guide arm includes a control link or rocker and whose wheel-inner guide arm consists of a bending-elastic spring leaf arranged in the transverse direction.
It is the object of the present invention to provide an improved rear axle suspension for a motor vehicle, by means of which an adjustment of the wheel toe-in and of the wheel camber is possible in a simple manner and in which the wheel under the interaction of forces is adjustable elastokinematically in the direction of toe-in and toe-out when driving straight and when driving through curves.
The underlying problems are solved according to the present invention in that the wheel guide member includes a spring strut connected with a guide body by way of a wheel-adjusting device, whereby the spring strut is constructed as part of a wheel-inner guide member and is positioned obliquely to the vehicle longitudinal center axis, whereby the spring strut as part of the wheel-inner guide member has a lesser length than an adjoining rigid guide part of the guide member and is constructed elastically deflectable, and whereby the spring strut retains the wheel-outer guide arm which is constructed in one piece with the guide body, so as to be displaceable within limits by way of the control bearing support on the body side.
The advantages essentially achieved with the present invention reside in that a wheel suspension is created which adjusts the vehicle wheel under the interaction of forces in a track-correcting manner. Thus, in the cooperation of the control bearing support on the body side of the wheel-outer rigid guide arm with the wheel-inner guide arm constructed as spring strut, a defined toe-out and toe-in adjustment of the wheel is possible in case of curve- and straight drives which is controllable by the joints on the body side forming an imaginary wheel guide pole.
The wheel-inner guide member includes a spring strut retained at its end at the vehicle body in a joint whereby the spring strut is connected with a rigid guide arm that is constructed in one piece with the guide body, by way of a wheel-adjusting device. The spring strut is constructed relatively short and has such a shape that over the entire length of the spring strut, a rigidity is coordinated corresponding to the loads and stresses which occur over this length, whereby this dimensioning takes place from the point of view of the maximum elasticity.
An elastic wheel adjustment with a limitation during the drive takes place by way of a body-side control bearing support at the wheel-outer guide arm which is provided with axial abutments and intentionally and deliberately limits the wheel toe-in and the wheel toe-out angle. In order that the adjustment of the wheel can take place only in the axial direction of the bearing support, it has a softer characteristic in the axial direction than in the radial direction.
The joint of the wheel-inner guide member is preferably constructed as ball joint which includes an elastic layer between an outer bearing shell and the ball. This joint forms essentially a rotary pole for the spring strut of the wheel guide member.
The wheel-adjusting device is arranged between the elastic spring strut and the adjoining rigid part of the guide member, which serves at the same time for the fastening of the spring strut at the adjoining rigid guide arm. This device includes eccentric elements to be adjusted from the inner side for toe-in and camber adjustment. The eccentric element for the camber adjustment together with further bolts serves at the same time for the fastening of the spring strut at the guide body.
In a wheel suspension with a guide arm arranged obliquely to the vehicle longitudinal center axis, it is for the most part difficult in constricted space conditions to so arrange a guide arm of larger dimension, for example, made as a cast part or the like, that no other body groups such as the seat trough, etc. are impaired. As a result of the relatively narrow spring strut arranged edge-wise, only a small amount of space is required within the area of this guide part so that the body groups do not experience any significant constriction.